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2021 Vol. 20 No. 8 Previous Issue    Next Issue

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Review
Crop Science
Horticulture
Plant Protection
Animal Science · Veterinary Medicine
Agro-ecosystem & Environment
Agricultural Economics and Management


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Fusarium graminearum is a predominant causal agent of Fusarium head blight (FHB) or scab on staple food crops including wheat, barley and maize in most growing areas. In addition to severe yield and economic losses, F. graminearum produces mycotoxins such as deoxynivalenol (DON) and zearalenone (ZEA) in the infected grains, which pose serious threats to human and animal health. Due to the lack of highly efficient disease-resistant cultivars, fungicides play a prominent role of reliable FHB management. However, with the development of resistance against fungicides, the efficiency of chemical control has been adversely affected. In order to establish efficient management strategies, a clear understanding of the pathogenesis of this devastating fungus seems particularly important. Nutrient and stress factor 1 (Nsf1), a transcription factor containing the classical Cys2-His2 (C₂H₂) zinc finger motif, is expressed under non-fermentable carbon conditions and in response to salt stress in Saccharomyces cerevisiae. However, the role of Nsf1 in filamentous fungi is not well understood. In this study, the orthologue of Nsf1 was investigated in F. graminearum (named FgNsf1), and the roles of FgNsf1 were elucidated by constructing a deletion mutant and its functional complementation mutant. The photo, provided by Prof. Chen Changjun from the Nanjing Agricultural University, China, shows the symptoms of FHB in the field induced by F. graminearum. See pages 2156–2169 in details.


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Review

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Natural nematicidal active compounds: Recent research progress and outlook CHEN Ji-xiang, SONG Bao-an 2021, 20(8): 2015-2031.  DOI: 10.1016/S2095-3119(21)63617-1 Abstract ( )   PDF in ScienceDirect   Plant-parasitic nematodes cause substantial economic losses to global agriculture yearly.  The use of nematicides is an effective way of controlling plant-parasitic nematodes.  However, the long-term use of traditional organophosphorus and carbamate chemical nematicides can lead to increased nematode resistance.  With the increasing awareness of the necessity for the protection of the environment and human health, highly toxic nematicides no longer meet the developmental requirements of modern agriculture.  Recently, many studies have been undertaken on the isolation and nematicidal activity of natural products against plant-parasitic nematodes and Caenorhabditis elegans.  As an important model nematode, C. elegans plays a vital reference role in studying plant-parasitic nematodes regarding nematicidal activity, metabolic mechanism, and modes of action and target.  We reviewed the latest research progress of natural nematicidal active compounds against plant-parasitic nematodes and C. elegans over the past ten years, discussed the structure-activity relationship and mechanism of action, and examined the development and application of natural nematicidal active compounds.

Crop Science

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Improving grain appearance of erect-panicle japonica rice cultivars by introgression of the null gs9 allele ZHAO Dong-sheng, LIU Jin-yu, DING Ai-qiu, ZHANG Tao, REN Xin-yu, ZHANG Lin, LI Qian-feng, FAN Xiao-lei, ZHANG Chang-quan, LIU Qiao-quan 2021, 20(8): 2032-2042.  DOI: 10.1016/S2095-3119(21)63659-6 Abstract ( )   PDF in ScienceDirect   The panicle architecture and grain size of rice affect not only grain yield but also grain quality, especially grain appearance. The erect-panicle (EP) trait controlled by the qpe9-1/dep1 allele has been widely used in high-yielding japonica rice breeding, but usually accompanied with moderate appearance of milled rice. The null gs9 allele shows a good potential for improving grain shape and appearance. However, GS9 and qPE9-1/DEP1 loci are tightly linked, and their interaction is unclear, which obviously restricts their utilization in modern rice breeding. In the present study, comparative analyses of protein and mRNA levels revealed that GS9 and qPE9-1 function independently. Three near-isogenic lines (NILs) carrying various allelic combinations of these two loci, NIL (gs9/qpe9-1), NIL (GS9/qPE9-1) and NIL (gs9/qPE9-1), in the EP japonica cultivar 2661 (GS9/qpe9-1) background were developed for genetic interaction analysis. GS9 and qPE9-1 had additive effects on determining grain size, and the null gs9 allele could decrease grain chalkiness and improve grain appearance without affecting plant and panicle architecture in EP japonica cultivars. Additionally, introgression lines (ILs) developed in another released EP japonica cultivar Wuyujing 27 (WYJ27) background showed the same additive effect and the feasibility of utilizing the gs9 allele to improve grain appearance quality in high-yielding EP cultivars. This study provides an effective strategy for rice breeders to improve rice grain appearance in EP japonica and related cultivars.

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Comparative transcriptome analysis of different nitrogen responses in low-nitrogen sensitive and tolerant maize genotypes DU Qing-guo, YANG Juan, Shah SYED MUHAMMAD SADIQ, YANG Rong-xin, YU Jing-juan, LI Wen-xue 2021, 20(8): 2043-2055.  DOI: 10.1016/S2095-3119(20)63220-8 Abstract ( )   PDF in ScienceDirect   Although previous researches have greatly increased our general knowledge on plant responses to nitrogen (N) stress, a comprehensive understanding of the different responses in crop genotypes is still needed.  This study evaluated 304 maize accessions for low-N tolerance under field conditions, and selected the low-N sensitive Ye478 and low-N tolerant Qi319 for further investigations.  After a 5-day low-N treatment, the typical N-deficient phenotype with yellowing older leaves was observed in Ye478 but not in Qi319.  After the 5-day low-N stress, 16 RNA libraries from leaf and root of Ye478 and Qi319 were generated.  The differentially expressed genes (DEGs) in the root of Qi319 up-regulated by special N deficiency were mainly enriched in energy-related metabolic pathways, including tricarboxylic acid metabolic process and nicotinamide metabolic process.  Consistent with yellowing older leaves only observed in Ye478, the special N deficiency-responsive DEGs related to thylakoid, chloroplast, photosynthetic membrane, and chloroplast stroma pathways were repressed by low-N stress in Ye478.  A total of 216 transcription factors (TFs), including ZmNLP5, were identified as special N deficiency-responsive TFs between Qi319 and Ye478, indicating the importance of transcriptional regulation of N stress-responsive pathway in different tolerance to low-N stress between crop genotypes.  In addition, 15 miRNAs were identified as DEGs between Qi319 and Ye478.  Taken together, this study contributes to the understanding of the genetic variations and molecular basis of low-N tolerance in maize.

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Identification of blast-resistance loci through genome-wide association analysis in foxtail millet (Setaria italica (L.) Beauv.) LI Zhi-jiang, JIA Guan-qing, LI Xiang-yu, LI Yi-chu, ZHI Hui, TANG Sha, MA Jin-feng, ZHANG Shuo, LI Yan-dong, SHANG Zhong-lin, DIAO Xian-min 2021, 20(8): 2056-2064.  DOI: 10.1016/S2095-3119(20)63196-3 Abstract ( )   PDF in ScienceDirect   Blast disease caused by the fungus Magnaporthe grisea results in significant yield losses of cereal crops across the world.  To date, very few regulatory genes contributing to blast resistance in grass species have been identified and the genetic basis of blast resistance in cereals remains elusive.  Here, a core collection of foxtail millet (Setaria italica) containing 888 accessions was evaluated through inoculation with the blast strain HN-1 and a genome-wide association study (GWAS) was performed to detect regulators responsible for blast disease resistance in foxtail millet.  The phenotypic variation of foxtail millet accessions inoculated with the blast strain HN-1 indicated that less than 1.60% of the samples were highly resistant, 35.25% were moderately resistant, 57.09% were moderately susceptible, and 6.08% were highly susceptible.  The geographical pattern of blast-resistant samples revealed that a high proportion of resistant accessions were located in lower latitude regions where the foxtail millet growing season has higher rain precipitation.  Using 720 000 SNP markers covering the Setaria genome, GWAS showed that two genomic loci from chromosomes 2 and 9 were significantly associated with blast disease resistance in foxtail millet.  Finally, eight putative genes were identified using rice blast-related transcriptomic data.  The results of this work lay a foundation for the foxtail millet blast resistance biology and provide guidance for breeding practices in this promising crop species and other cereals.

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Comparison of grain yield and quality of different types of japonica rice cultivars in the northern Jiangsu plain, China BIAN Jin-long, REN Gao-lei, XU Fang-fu, ZHANG Hong-cheng, WEI Hai-yan 2021, 20(8): 2065-2076.  DOI: 10.1016/S2095-3119(20)63348-2 Abstract ( )   PDF in ScienceDirect   In recent years, an increasing number of different types of japonica rice cultivars have been released in the southern rice region of China.  The grain yield and quality of these new cultivars showed significant differences in large scale planting.  However, the causes of the differences remain little known.  Therefore, three typical types of japonica rice cultivars were used in this study to investigate their grain yield and quality.  A scanning calorimeter (DSC), X-ray powder diffractometer (XRD), rapid viscosity analyzer (RVA) and taste analyzer were used to evaluate the cooking and eating properties.  The results showed that the yield of non-soft hybrid japonica rice cultivars was significantly higher than that of non-soft inbred japonica rice cultivars and soft inbred japonica rice cultivars.  Soft inbred japonica rice cultivars had a low amylose content and moderate protein content, which are the main reasons for the superior cooking and eating quality.  In addition, the relative crystallinity of soft inbred japonica rice cultivars was significantly higher than that of non-soft inbred and non-soft hybrid japonica rice cultivars, which is considered the major factor resulting in higher transition temperature and gelatinization enthalpy (ΔHgel).  Non-soft hybrid japonica rice cultivars had a higher number of large starch granules than soft inbred and non-soft inbred japonica rice cultivars.  The setback value (SB) and breakdown value (BD), indirectly reflecting the cooking and eating quality of the three types of japonica rice cultivars, also confirmed that soft inbred japonica rice cultivars with a low SB value and a high BD value had better palatability than the other two types.  This study provides guidance for future plantation of different types of japonica rice cultivars in large rice-producing areas.

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Lignin metabolism regulates lodging resistance of maize hybrids under varying planting density LI Bin, GAO Fei, REN Bai-zhao, DONG Shu-ting, LIU Peng, ZHAO Bin, ZHANG Ji-wang 2021, 20(8): 2077-2089.  DOI: 10.1016/S2095-3119(20)63346-9 Abstract ( )   PDF in ScienceDirect   Hybrids and planting density are the main factors affecting maize lodging resistance.  Here, we aimed to elucidate the mechanism of the regulation of maize lodging resistance by comparing two hybrids at various planting densities from the perspective of lignin metabolism.  Our results showed that compared to lodging-susceptible hybrid Xundan 20 (XD20), lodging-resistant hybrid Denghai 605 (DH605) showed a lower center of gravity and culm morphological characteristics that contributed to the higher lodging resistance of this hybrid.  Lignin content, activities of key lignin synthesis-related enzymes and G-, S- and H-type monomer contents were significantly higher in hybrid DH605 than in hybrid XD20.  Stalk mechanical strength, lignin accumulation and enzyme activity decreased significantly with increasing planting density in the two hybrids.  While G-type monomers first decreased with increasing planting density but then remained stable, S-type monomers showed a decreasing trend, and H-type monomers showed an increasing trend.  Correlation analysis showed that lodging rate was significantly correlated with plant traits and lignin metabolism.  Therefore, maize hybrids characterized by high lignin accumulation, high lignin synthesis-related activities, high S-type monomer content, low center of gravity, high stem puncture strength, high cortical thickness, and small vascular bundle area are more resistant to lodging.  High planting densities reduce stalk lignin accumulation, relevant enzyme activities and mechanical strength, thereby, ultimately increasing the lodging rate significantly.

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Effects of plant density and nitrogen rate on cotton yield and nitrogen use in cotton stubble retaining fields WANG Shi-hong, MAO Li-li, SHI Jia-liang, NIE Jun-jun, SONG Xian-liang, SUN Xue-zhen 2021, 20(8): 2090-2099.  DOI: 10.1016/S2095-3119(20)63323-8 Abstract ( )   PDF in ScienceDirect   Increasing nitrogen (N) rate could accelerate the decomposition of crop residues, and then improve crop yield by increasing N availability of soil and N uptake of crops.  However, it is not clear whether N rate and plant density should be modified after a long period of cotton stubble return with high N rate.  This study seeks to assess the effects of N rate and plant density on cotton yield, N use efficiency, leaf senescence, soil inorganic N, and apparent N balance in cotton stubble return fields in Liaocheng, China, in 2016 and 2017.  Three plant densities 5.25 (D5.25), 6.75 (D6.75) and 8.25 (D8.25) plants m–2 and five N rates 0 (N0), 105 (N105), 210 (N210), 315 (N315), and 420 (N420) kg ha–1  were investigated.  Compared to the combination used by local farmers (D5.25N315), a 33.3% N reduction and a 28.6% increase in plant density (D6.75N210) can maintain high cotton yield, while a 66.7% N reduction at 6.75 plants m–2 (D6.75N105) can only achieve high yield in the first year.  Biological yield increased with the increase of N rate and plant density, and the highest yield was obtained under 420 kg N ha–1 at 8.25 plants m–2 (D8.25N420) across the two years under investigation.  Compared to D5.25N315, N agronomic efficiency (NAE) and N recovery efficiency (NRE) in D6.75N210 increased by 30.2 and 54.1%, respectively, and NAE and NRE in D6.75N210 increased by 104.8 and 88.1%, respectively.  Soil inorganic N decreased sharply under 105 kg N ha–1, but no change was found under 210 kg N ha–1 at 6.75 plants m–2.  N deficit occurred under 105 kg N ha–1, but it did not occurr under 210 kg N ha–1 at 6.75 plants m–2.  Net photosynthetic rate and N concentration of leaves under N rate ranging from 210 to 420 kg ha–1 were higher than those under N rate of 0 or 105 kg N ha–1 at all three densities.  The findings suggest that D6.75N210 is a superior combination in cotton stubble retaining fields in the Yellow River Valley and other areas with similar ecologies.

Horticulture

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Mapping and predicting a candidate gene for flesh color in watermelon WANG Chao-nan, LUAN Fei-shi, LIU Hong-yu, Angela R. DAVIS, ZHANG Qi-an, DAI Zu-yun, LIU Shi 2021, 20(8): 2100-2111.  DOI: 10.1016/S2095-3119(20)63487-6 Abstract ( )   PDF in ScienceDirect   The color of watermelon flesh is an important trait determined by a series of carotenoids.  Herein, we used Cream of Saskatchewan (pale yellow flesh) and PI 186490 (white flesh) as parental materials for an F2 segregation and initial mapping using the bulked segregant analysis sequencing (BSA-seq) strategy.  The BSA results revealed a flesh color-related QTL  that spans approximately 2.45 Mb on chromosome 6.  This region was preliminarily positioned in a 382-kb segment, and then narrowed down into a 66.8-kb segment with 1 260 F2 individuals.  A total of nine candidate genes were in the fine mapping interval, but only Cla007528 (encoding chlorophyllase) had non-synonymous mutations and was significantly expressed between the parental materials throughout flesh development.  We also checked the expression patterns of the carotenoid metabolic pathway genes based on RNA-seq data and qRT-PCR validation.  Three genes in the xanthophyll cycle (ClCHYB, ClNCED-1 and ClNCED-7) exhibited differential expression patterns between the two parental lines at different flesh color formation stages.  ClPSY1, ClPDS, ClZDS, ClCHXE, ClCRTISO and ClLCYB also exhibited clearly different expression patterns accompanied by carotenoid accumulation.

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Genome-wide identification, molecular evolution, and expression divergence of the hexokinase gene family in apple ZHU Ling-cheng, SU Jing, JIN Yu-ru, ZHAO Hai-yan, TIAN Xiao-cheng, ZHANG Chen, MA Feng-wang, LI Ming-jun, MA Bai-quan 2021, 20(8): 2112-2125.  DOI: 10.1016/S2095-3119(20)63562-6 Abstract ( )   PDF in ScienceDirect   Hexokinase (HXK) is the first irreversible catalytic enzyme in the glycolytic pathway, which not only provides energy for plant growth and development but also serves as a signaling molecule in response to environmental changes.  However, the evolutionary pattern of the HXK gene family in apple remains unknown.  In this study, a total of nine HXK genes were identified in the Malus×domestica genome GDDH13 v1.1.  The physiological and biochemical properties, exon-intron structures, conserved motifs, and cis-elements of the MdHXK genes were determined.  Predicted subcellular localization indicated that the MdHXK genes were mainly distributed in the mitochondria, cytoplasm, and nucleus.  Gene duplication revealed that whole-genome duplication (WGD) and segmental duplication played vital roles in MdHXK gene family expansion.  The ω values of pairwise MdHXK genes indicated that this family was subjected to strong purifying selection during apple domestication.  Additionally, five subfamilies were classified, and recent/old duplication events were identified based on phylogenetic tree analysis.  Different evolutionary rates were estimated among the various HXK subfamilies.  Moreover, divergent expression patterns of the MdHXK genes in four source-sink tissues and at five different apple fruit developmental stages indicated that they play vital roles in apple fruit development and sugar accumulation.  Our study provides a theoretical basis for future elucidation of the biological functions of the MdHXK genes during apple fruit development.

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Preharvest application of melatonin induces anthocyanin accumulation and related gene upregulation in red pear (Pyrus ussuriensis) SUN Hui-li, WANG Xin-yue, SHANG Ye, WANG Xiao-qian, DU Guo-dong, LÜ De-guo 2021, 20(8): 2126-2137.  DOI: 10.1016/S2095-3119(20)63312-3 Abstract ( )   PDF in ScienceDirect   Anthocyanins are important components in the peel of red pears and contribute to the appearance of the fruit.  Melatonin application is known to affect anthocyanin biosynthesis, but the effect of preharvest melatonin application on fruit coloration remains largely unknown.  The objective of this study was to determine the effects of preharvest melatonin application on pigmentation, phenolic compounds, and the expression of related genes in Nanhong pear (Pyrus ussuriensis).  The applications were performed during the pre-color-change period by spraying 50 or 200 μmol L–1 of melatonin on fruits.  We found that treatment with melatonin had a significant effect on color development.  The concentrations of anthocyanins and favonols were enhanced by melatonin treatment, whereas hydroxycinnamate and favanol concentrations were reduced.  Quantitative real-time PCR analyses indicated that the transcription levels for most anthocyanin biosynthetic genes and anthocyanin-related transcription factors were induced by melatonin.  Melatonin application also stimulated the expression of melatonin biosynthesis-related genes and consequently caused an increase in endogenous melatonin concentration.  These results provide insights into melatonin-induced fruit coloration and will facilitate the application of exogenous melatonin in agriculture.

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Genome-wide identification and expression analysis of Argonaute gene family from longan embryogenic callus CHEN Rong-zhu, SHEN Xu, ZHANG Shu-ting, ZHAO Hua, CHEN Xiao-hui, XU Xiao-ping, HUO Wen, ZHANG Zi-hao, LIN Yu-ling, LAI Zhong-xiong 2021, 20(8): 2138-2155.  DOI: 10.1016/S2095-3119(20)63313-5 Abstract ( )   PDF in ScienceDirect   Argonaute (AGO) proteins are the core of the RNA-induced gene silencing complex which regulate a wide variety of processes in plants, from organ development to abiotic stress responses.  They have been identified in many plants, but little is known in longan (Dimocarpus longan Lour.), and how AGO functions in the signaling pathways in plant embryos in response to changing environmental stimuli remains unclear.  In the present research, a genome-wide analysis of the AGO gene family members and their roles in somatic embryogenesis (SE), zygotic embryogenesis (ZE), tissue developmental processes, and responses to hormones, light and abiotic stress in longan were conducted.  Ten longan AGO genes were identified genome-wide and divided into four clades.  They were distributed on chromosomes 1, 4, 8, 10, 12, 13, 14, and 15, and had 2–23 introns.  The expression profiling implied that DlAGOs regulated early and middle embryogenesis, as well as developmental processes of seed, flower, and stem in longan.  In addition, the transcript levels of DlAGOs in response to exogenous hormones, light and abiotic stress showed differences in expression patterns.  These results provide the useful information for further elucidation of RNAi-mediated gene silencing in longan embryogenic callus (EC).

Plant Protection

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The transcription factor FgNsf1 regulates fungal development, virulence and stress responses in Fusarium graminearum SHI Dong-ya, REN Wei-chao, WANG Jin, ZHANG Jie, Jane Ifunanya MBADIANYA, MAO Xue-wei, CHEN Chang-jun 2021, 20(8): 2156-2169.  DOI: 10.1016/S2095-3119(20)63339-1 Abstract ( )   PDF in ScienceDirect   Nutrient and stress factor 1 (Nsf1), a transcription factor containing the classical Cys2-His2 (C2H2) zinc finger motif, is expressed under non-fermentable carbon conditions and in response to salt stress in Saccharomyces cerevisiae.  However, the role of Nsf1 in filamentous fungi is not well understood.  In this study, the orthologue of Nsf1 was investigated in Fusarium graminearum (named FgNsf1), a causal agent of Fusarium head blight (FHB).  The functions of FgNsf1 were evaluated by constructing a FgNSF1 deletion mutant, designated as ΔFgNsf1, and its functional complementation mutant ΔFgNsf1-C.  Gene deletion experiments showed that the mycelial growth rate, asexual and sexual reproduction of ΔFgNsf1 were significantly reduced, but the pigment production of ΔFgNsf1 was remarkably increased compared with the PH-1 and ΔFgNsf1-C.  In addition, the tolerance of ΔFgNsf1 to osmotic pressures, cell wall-damaging agents and oxidative stress increased significantly.  Sensitivity tests to different fungicides revealed that ΔFgNsf1 exhibited increased sensitivity to carbendazim (MBC) and tebuconazole, and enhanced tolerance to fludioxonil and iprodione than PH-1 and ΔFgNsf1-C.  The virulence of ΔFgNsf1 to wheat coleoptiles and flowering wheat heads were dramatically decreased, which was consistent with the decrease in the yield of deoxynivalenol (DON).  All of these defects were restored by target gene complementation.  These results indicated that FgNsf1 plays a crucial role in vegetative growth, asexual and sexual reproduction, stress responses, fungicide sensitivity, and full virulence in F. graminearum.

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Robust molecular detection of the new Tomato brown rugose fruit virus in infected tomato and pepper plants from Turkey Hakan FIDAN, Pelin SARIKAYA, Kubra YILDIZ, Bengi TOPKAYA, Gozde ERKIS, Ozer CALIS 2021, 20(8): 2170-2179.  DOI: 10.1016/S2095-3119(20)63335-4 Abstract ( )   PDF in ScienceDirect   Tomato brown rugose fruit virus (ToBRFV) causes severe fruit loss in tomato (Solanum lycopersicum) and pepper (Capsicum annuum) plants.  It is an emerging Tobamovirus that is spreading globally.  The major challenge is to develop a reliable method for the detection of the virus, and to better characterize the symptoms it causes.  The aims of this study, therefore, were to characterize the symptom development on tomato and pepper plants, and to establish a reliable detection method for the virus.  Following infection of the tomato and pepper plants with ToBRFV, the leaves turned chlorotic, mosaic or mottled, while the fruit became rugose, necrotic and marbled, and showed discoloration with yellow or brown spots.  Transmission electron microscopy (TEM) revealed single rod-like virus particles characteristic of the Tobamoviruses.  Classical reverse transcription PCR (RT-PCR) and quantitative PCR (qPCR) with specific primers and probes confirmed that the virus is ToBRFV.  We found that the resistance genes from tomato, Tm-22, and pepper, L1, L2, L3 and L4, did not confer resistance to ToBRFV.  Here, we present a PCR-based method as a diagnostic test for detecting ToBRFV in infected seeds.  This method will help to prevent further spread of the virus in commercial seeds.

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Transcriptomic analysis reveals the transcription factors involved in regulating the expression of EPSPS gene, which confers glyphosate resistance of goosegrass (Eleusine indica) ZHANG Chun, YU Chao-jie, ZHANG Tai-jie, GUO Wen-lei, TIAN Xing-shan 2021, 20(8): 2180-2194.  DOI: 10.1016/S2095-3119(21)63682-1 Abstract ( )   PDF in ScienceDirect   Glyphosate inhibits the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) and overexpression of the EPSPS gene is one of the molecular mechanisms conferring glyphosate resistance in weeds.  A regulatory sequence of EPSPS gene was isolated previously, and an alteration in its 5´-untranslated region (UTR) pyrimidine (Py)-rich stretch element is involved in the regulation of EPSPS expression in glyphosate-resistant (GR) Eleusine indica.  However, the transcription factors involved in this regulatory sequence remain to be elucidated.  In this study, we investigated the regulatory network of EPSPS overexpression associated genes in a GR E. indica population by RNA-seq.  The differentially expressed transcript analyses revealed that glyphosate treatment caused an increase in the expression of 2 752 unigenes and a decrease in the expression of 4 025 unigenes in the GR E. indica, compared to the glyphosate-susceptible (GS) E. indica.  Among them, 1 373 unigenes were identified to be co-expressed with the EPSPS gene in GR E. indica.  GO and KEGG pathway analyses showed that the up-regulated unigenes were mainly enriched in chloroplasts and associated with the shikimate biosynthesis pathway, chlorophy II and peroxisome metabolism processes.  Notably, the expression of a Shikimate kinase which catalyzed the conversion of Shikimate to Shikimate 3-phosphate (S3P, a substrate of EPSPS), was also up-regulated.  Eight transcription factors were identified as likely to be involved in the regulation of the EPSPS expression, and three of them (ARF2, ARF8 and BPC6) showed more binding sites because of a (CT)n insertion of the 5´-UTR Py-rich stretch element in GR.  However, the yeast one-hybrid assay illustrated that ARF8 and BPC6 could bind to the 5´-UTR Py-rich stretch element of wild type EPSPS, but could not bind to the mutated form.  Our data suggests that the transcriptional regulation of EPSPS expression is complex and was significantly altered in GR E. indica.  These discoveries provide new references for further study of the EPSPS overexpression mechanism that endows glyphosate resistance.

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Effects of inhibitors on the protease profiles and degradation of activated Cry toxins in larval midgut juices of Cnaphalocrocis medinalis (Lepidoptera: Pyralidae) YANG Ya-jun, XU Hong-xing, WU Zhi-hong, LU Zhong-xian 2021, 20(8): 2195-2203.  DOI: 10.1016/S2095-3119(20)63316-0 Abstract ( )   PDF in ScienceDirect   Midgut juice plays an important role in food digestion and detoxification in insects.  In order to understand the potential of midgut juice of Cnaphalocrocis medinalis (Guenée) to degrade Bt proteins, the enzymatic activity of midgut juice and its degradation of Bt proteins (Cry2A, Cry1C, Cry1Aa, and Cry1Ac) were evaluated in this study through protease inhibitor treatments.  The activities of total protease in midgut juices were significantly inhibited by phenylmethylsulfonyl fluoride (PMSF), tosyl-L-lysine chloromethyl ketone (TLCK), pepstatin A and leupeptin.  The enzymatic activity of chymotrypsin was significantly inhibited by PMSF, and enzymatic activity of trypsin was significantly inhibited by ethylenediaminetetraacetic acid (EDTA), PMSF, tosyl phenylalanine chloromethyl ketone (TPCK), TLCK and trans-epoxysuccinyl-L-leucylamido-(4-guanidino) butane (E-64).  EDTA could significantly inhibit the degradation of Cry2A by C. medinalis.  EDTA, PMSF, TPCK, and TLCK could inhibit the degradation of Cry1C and Cry1Aa.  EDTA, PMSF, TPCK, TLCK, and E-64 could inhibit the degradation of Cry1Ac.  Our results indicated that some protease inhibitors hindered various enzymatic activities in the larval midgut of C. medinalis, which may reduce the insect’s ability to degrade Bt toxins.  These findings may aid the application of protease inhibitors in the management of this insect pest in the future.

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Identification and tissue distribution of odorant binding protein genes in Harmonia axyridis (Coleoptera: Coccinellidae) QU Cheng, WANG Ran, CHE Wu-nan, LI Feng-qi, ZHAO Hai-peng, WEI Yi-yun, LUO Chen, XUE Ming 2021, 20(8): 2204-2213.  DOI: 10.1016/S2095-3119(20)63297-X Abstract ( )   PDF in ScienceDirect   The olfactory system of insects is crucial in modulating behaviors such as host seeking, mating, and oviposition.  Odorant-binding proteins (OBPs) are involved in semiochemical recognition.  OBPs recognize and bind odorants and transport them to odorant receptors located in olfactory neurons.  Harmonia axyridis (Coleoptera: Coccinellidae) is a widely used predacious biological control agent for many agricultural and forestry pests.  This study identified 19 OBPs in H.?axyridis based on the antennal and whole-body transcriptomes of adults and obtained all the full-length open reading frames, including 11 ‘Classic’ OBPs, 7 ‘Minus-C’ OBPs and 1 ‘Plus-C’ OBP.  They encoded 125 to 241 amino acid proteins with molecular weights ranging from 13.75 to 27.75 kDa and isoelectric points ranging from 4.15 to 8.80.  Phylogenetic analyses were used to study the relationships between H.?axyridis OBPs and OBPs from other species of Coleoptera.  Quantitative real-time PCR (qPCR) analysis showed that HaxyOBP2, 3, 5, 8, 10, 12, 13, 14, and 15 were highly expressed in antennae of both adult females and males.  Moreover, HaxyOBP2, 3, 5, 12, and 15 were more abundantly expressed in antennae than other body parts, while HaxyOBP13 and HaxyOBP14 were expressed predominantly, and at similar levels, in the head and antennae.  The other OBP genes were highly expressed in non-olfactory tissues including the thorax, abdomen, legs, and wings.  These results provide valuable information for further study of H.?axyridis olfaction, which may ultimately enhance its use as a biocontrol agent.

Animal Science · Veterinary Medicine

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Effects of formic acid and corn flour supplementation of banana pseudostem silages on nutritional quality of silages, growth, digestion, rumen fermentation and cellulolytic bacterial community of Nubian black goats Zhang Hao, Cheng Xuan, Mabrouk ELSABAGH, Lin Bo, Wang Hong-rong 2021, 20(8): 2214-2226.  DOI: 10.1016/S2095-3119(20)63470-0 Abstract ( )   PDF in ScienceDirect   The objective of this study was to evaluate the effects of adding formic acid and corn flour supplementation to banana pseudostem silages on the nutritional quality of these silages, growth, digestion, rumen fermentation and cellulolytic bacterial community of Nubian black goats fed these silages.  Banana pseudostem silage was prepared either conventionally without any additives (CON) or mixed with 0.6% formic acid (F), 10% corn flour (C), or both (F+C).  Four experimental diets containing 40% of the corresponding silages were designed with roughage to concentrate ratio of 50:50 (dry matter (DM) basis).  A total of 48 Nubian black castrated goats (body weight (BW), (22.64±1.82) kg; 4-mon-old) were randomized into one of the four treatment groups with 12 replicates of one castrated goat per replicate for each treatment in a completely randomized design.  Each group was fed on one of the four experimental diets for 40 days.  A factorial arrangement of treatments of 2 (formic acid levels: 0 and 0.6%)×2 (corn flour: 0 and 10%) was adopted.  Formic acid supplementation increased (P<0.05) average daily gain, as well as lactic acid, propionate and butyric acid and water-soluble carbohydrate concentrations, but decreased (P<0.05) the feed conversion rate, pH value, acetate/propionate ratio, and butyric acid concentration relative to the CON group.  Corn flour supplementation increased (P<0.05) the apparent digestibility of crude protein, neutral detergent fiber, and non-fibrous carbohydrate and Fibrobacter succinogenes, Ruminococcus albus, and Butyrivibrio fibrisolvens populations, but decreased (P<0.05) the Ruminococcus flavefaciens population relative to the CON group.  There were no F×C treatment interactions (P>0.05) for any of the other indices except for the apparent digestibility of non-fibrous carbohydrate (NFC) (P<0.05).  The results demonstrated that adding 0.6% formic acid and 10% corn flour supplementation to banana pseudostem silages improved the nutritional quality of these silages and enhanced the growth performance of Nubian black castrated goats by improving apparent nutrient digestibility, and regulating ruminal fermentation and bacteria populations.

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Kaempferol inhibits Pseudorabies virus replication in vitro through regulation of MAPKs and NF-κB signaling pathways CHEN Xu, CHEN Ya-qin, YIN Zhong-qiong, WANG Rui, HU Huai-yue, LIANG Xiao-xia, HE Chang-liang, YIN Li-zi, YE Gang, ZOU Yuan-feng, LI Li-xia, TANG Hua-qiao, JIA Ren-yong, SONG Xu 2021, 20(8): 2227-2239.  DOI: 10.1016/S2095-3119(20)63477-3 Abstract ( )   PDF in ScienceDirect   Pseudorabies virus (PRV), in the family Herpesviridae, is a pathogen of Aujeszky’s disease, which causes great economic losses to the pig industry.  Recent outbreaks of Pseudorabies imply that new control measures are urgently needed.  The present study shows that kaempferol is a candidate drug for controlling PRV infection, as it possesses the ability to inhibit PRV replication in a dose-dependent manner in vitro.  Kaempferol at a concentration of 52.40 μmol L–1 could decrease PRV-induced cell death by 90%.  With an 50% inhibitory concentration (IC50) value of 25.57 μmol L–1, kaempferol was more effective than acyclovir (positive control) which has an IC50 value of 54.97 μmol L–1.  A mode of action study indicated that kaempferol inhibited viral penetration and replication stages, decreasing viral loads by 4- and 30-fold, respectively.  Addition of kaempferol within 16 h post infection (hpi) could significantly inhibit virus replication, and viral genome copies were decreased by almost 15-fold when kaempferol was added at 2 hpi.  Kaempferol regulated the NF-κB and MAPKs signaling pathways involved in PRV infection and changed the levels of the target genes of the MAPKs (ATF-2 and c-Jun) and NF-κB (IL-1α, IL-1β and IL-2) signaling pathways.  The findings of the current study suggest that kaempferol could be an alternative measure to control PRV infection.

Agro-ecosystem & Environment

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Nitrogen acquisition, fixation and transfer in maize/alfalfa intercrops are increased through root contact and morphological responses to interspecies competition SHAO Ze-qiang, ZHENG Cong-cong, Johannes A. POSTMA, LU Wen-long, GAO Qiang, GAO Ying-zhi, ZHANG Jin-jing 2021, 20(8): 2240-2254.  DOI: 10.1016/S2095-3119(20)63330-5 Abstract ( )   PDF in ScienceDirect   Nitrogen (N) fixation by legumes and nitrogen transfer to cereals have been considered as important pathways for overyielding and higher N use efficiency in cereal/legume intercropping systems.  However, the extent to which root morphology contributes to N fixation and transfer is unclear.  A two-factorial greenhouse experiment was conducted to quantify the N fixation, transfer and root morphology characteristics of the maize/alfalfa intercropping system in two consecutive years using the 15N-urea leaf labeling method, and combining two N levels with three root separation techniques.  N application could inhibit N fixation and transfer in a maize/alfalfa intercropping system.  Irrespective of the N application level, compared with plastic sheet separation (PSS), no separation (NS) and nylon mesh separation (NNS) significantly increased the total biomass (36%) and total N content (28%), while the N fixation rate also sharply increased by 75 to 134%, and the amount of N transferred with no root barrier was 1.24–1.42 times greater than that with a mesh barrier.  Redundancy analysis (RDA) showed that the crown root dry weight (CRDW) of maize and lateral root number (LRN) of alfalfa showed the strongest associations with N fixation and transfer.  Our results highlight the importance of root contact for the enhancement of N fixation and transfer via changes in root morphology in maize/alfalfa intercropping systems, and the overyielding system was achieved via increases in maize growth, at the cost of smaller decreases in alfalfa biomass production.

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Functional diversity of soil microbial communities in response to supplementing 50% of the mineral N fertilizer with organic fertilizer in an oat field ZHANG Mei-jun, JIA Ju-qing, LU Hua, FENG Mei-chen, YANG Wu-de 2021, 20(8): 2255-2264.  DOI: 10.1016/S2095-3119(20)63331-7 Abstract ( )   PDF in ScienceDirect   The effects of supplementing 50% of the mineral N fertilizer with organic fertilizer on the metabolism and diversity of soil microbial communities in an oat field were investigated using Biolog-Eco plates.  The experiment consisted of five treatments: no fertilizer (CK), mineral N fertilizer applied at 90 and 45 kg ha–1 N in the form of urea (U1 and U2, respectively), and U2 supplemented with organic fertilizer  in the form of sheep manure at 90 and 45 kg ha–1 N (U2OM1 and U2OM2, respectively).  Each treatment had three replications.  The experiment was conducted in 2018 and 2019 in Pinglu District, Shanxi Province, China.  The carbon source utilization by soil microbial communities, such as amino acids, amines, carbohydrates, carboxylic acids, and polymers, increased when 50% of the mineral N fertilizer was replaced with organic fertilizer in both years.  This result was accompanied by increased richness, dominance, and evenness of the microbial communities.  The utilization of amino acid, amine, and carboxylic acid carbon sources and community evenness were further improved when the organic fertilizer amount was doubled in both years.  Biplot analysis indicated that amines and amino acids were the most representative of the total carbon source utilization by the soil microbial communities in both years.  The highest oat yield was achieved at a total N application rate of 135 kg ha–1 in the treatment involving 45 kg ha–1 N in the form of urea and 90 kg ha–1 N in the form of sheep manure in both years.  It was concluded that the application of 50% of the conventional rate of mineral N fertilizer supplemented with an appropriate rate of organic fertilizer enhanced both the functional diversity of soil microbial communities and oat yield.  Amine and amino acid carbon sources may be used as a substitute for total carbon sources for assessing total carbon source utilization by soil microbial communities in oat fields in future studies. Keywords:

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Effects of long-term straw incorporation on nematode community composition and metabolic footprint in a rice–wheat cropping system CHEN Yun-feng, XIA Xian-ge, HU Cheng, LIU Dong-hai, QIAO Yan, LI Shuang-lai, FAN Xian-peng 2021, 20(8): 2265-2276.  DOI: 10.1016/S2095-3119(20)63435-9 Abstract ( )   PDF in ScienceDirect   Soil nematode communities can provide valuable information about the structure and functions of soil food webs, and are sensitive to agricultural practices, including short-term straw incorporation.  However, currently, such effects under long-term straw incorporation conditions at different fertility levels are largely unknown.  Thus, we conducted a 13-year ongoing experiment to evaluate the effects of long-term straw incorporation on the structure and functions of the soil food web in low and high fertility soils through analyzing its effects on nematode communities, food web indices and metabolic footprints.  Four treatments were included: straw removal (–S) under non-fertilized (–NPK) or fertilized (+NPK) conditions; and straw incorporation (+S) under –NPK or +NPK conditions.  Soil samples from a 0–20 cm depth layer were collected when wheat and rice were harvested.  Compared with straw removal, straw incorporation increased the abundances of total nematodes, bacterivores, plant-parasites and omnivores-predators, as well the relative abundances of omnivores-predators with increases of 73.06, 89.29, 95.31, 238.98, and 114.61% in –NPK soils and 16.23, 2.23, 19.01, 141.38, and 90.23% in +NPK soils, respectively.  Regardless of sampling times and fertilization effects, straw incorporation increased the diversity and community stability of nematodes, as indicated by the Shannon-Weaver diversity index and maturity index.  Enrichment and structure index did not show significant responses to straw incorporation, but a slight increase was observed in the structure index.  The analysis of nematode metabolic footprints showed that straw incorporation increased the plant-parasite footprint and structure footprint by 97.27 and 305.39% in –NPK soils and by 11.29 and 149.56% in +NPK soils, but did not significantly influence enrichment, bacterivore and fungivore footprints.  In conclusion, long-term straw incorporation, particularly under a low fertility level, favored the soil nematodes and regulated the soil food web mainly via a top-down effect.

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The impacts of oxytetracycline on humification during manure composting can be alleviated by adjusting initial moisture contents as illustrated by NMR FENG Yao, WANG Gui-zhen, LIU Yuan-wang, CHENG Deng-miao, FAN Shuang-hu, ZHAO Quan-sheng, Jianming XUE, ZHANG Shu-qing, LI Zhao-jun 2021, 20(8): 2277-2288.  DOI: 10.1016/S2095-3119(20)63332-9 Abstract ( )   PDF in ScienceDirect   Oxytetracycline (OTC) residues have been found in soil and water, and they may pose potential risks to agricultural ecological environments.  One of the most impactful ways for OTC to enter the soil and water environments is through excrement used as organic fertilizer.  Therefore, it is important to remove OTC during manure composting and to understand the transformation of the organic materials during composting in the presence of OTC.  In the present paper, chicken manure and wheat sawdust spiked with OTC were composted under different initial moisture contents (MC) to evaluate the degradation of OTC and  changes of organic matter during the composting process.  The MC has a significant effect on OTC degradation during composting.  A higher MC of 65% was more conducive to OTC degradation (77.4%) and compost maturity compared to the lower MC.  However, the higher MC of 65% could increase the ammonia volatilization by promoting nitrification compared to the lower MC.  An increase in the initial MC could improve the composting temperature.  NMR results illustrated that the presence of OTC could affect the internal transformation of aliphatics, and OTC inhibited compost humification.  Thus, an initial MC of 55–65% can alleviate the impacts of OTC on humification during manure composting.

Agricultural Economics and Management

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African swine fever and meat prices fluctuation: An empirical study in China based on TVP-VAR model LI Hui-shang, HU Chen-pei, LÜ Zheng, LI Mei-qi, GUO Xin-zhu 2021, 20(8): 2289-2301.  DOI: 10.1016/S2095-3119(20)63307-X Abstract ( )   PDF in ScienceDirect   frican swine fever (ASF), a fatal disease outbroken in China in August 2018, has widely attracted social concern especially in the information era.  The occurrence of ASF led to an imbalance between supply and demand in pork and other meat markets.  As a result, meat prices fluctuated greatly during the past year in 2019.  To measure ASF quantitatively, the internet public concern index about ASF was created using web crawler methods.  The relationships between ASF and meat prices were analyzed based on time-varying parameter vector auto-regressive (TVP-VAR) model.  The results showed that there were some differences in the impact size, direction and duration of ASF on the prices of pork, chicken, beef and mutton, and the characteristics of time variability and heterogeneity were obvious.  At the same time, the impact of ASF on meat prices is not consistent with the trend and degree of ASF.  The impulse intensity is strongly correlated with the strength and duration of ASF, and it is generally weak in the early stage and much stronger in the middle and late periods.  The results indicate that macro regulations, monitoring and early-warning system, standardizing production and circulation, and the public opinion monitoring and guidance about ASF should be given more attention in future to stabilize the market expectations and to promote a smooth functioning of the livestock markets.

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Adoption of small-scale irrigation technologies and its impact on land productivity: Evidence from Rwanda Jules NGANGO, Seungjee HONG 2021, 20(8): 2302-2312.  DOI: 10.1016/S2095-3119(20)63417-7 Abstract ( )   PDF in ScienceDirect   In an attempt to identify solutions to the effects of erratic rainfall patterns and droughts that limit agricultural production growth, the Rwandan government has recently increased investments in irrigation development.  In this study, we analyze the adoption of small-scale irrigation technologies (SSITs) and its impact on land productivity using cross-sectional data from a sample of 360 farmers in Rwanda.  The study uses the propensity score matching technique to address potential self-selection bias.  Our results reveal that adoption decisions are significantly influenced by factors such as education, farm size, group membership, gender, extension services, access to credit, access to weather forecast information, risk perceptions, access to a reliable source of water for irrigation, awareness of rainwater harvesting techniques, and awareness of subsidy programs.  In addition, the results show that the adoption of SSITs has a significantly positive impact on land productivity.  The study concludes with policy implications that highlight the need to promote the adoption of SSITs among farmers as a strategy to improve agricultural productivity and food security in Rwanda.